The present invention relates to a display making use of plasma discharge, and particularly to a composition of an ionizable gas which fills a plasma cell of the display.
A feature of a display making use of plasma discharge is its flat structure. As such a display, there are known a PDP (plasma display panel) and a PALC (plasma addressed liquid crystal display). The PDP generates a display by exciting a fluorescent substance with the aid of plasma discharge. The PALC is a type of addressing of an optoelectric material such as liquid crystal with the aid of plasma discharge, as disclosed, for example, in Japanese Patent Laid-open No. Hei.4-265931. The plasma addressed liquid crystal display basically includes a flat panel structure having a display cell and a plasma cell which are stacked on each other with an intermediate substrate put therebetween. The display cell has an upper substrate joined to the intermediate substrate with a specific gap put therebetween, an optoelectric material such as liquid crystal kept in the gap, and signal electrodes formed on the upper substrate in rows to be applied with image signals. The plasma cell has a lower substrate joined to the intermediate substrate with a specific gap put therebetween for forming an enclosed space, an ionizable gas which fills the space, and scanning electrodes formed on the lower substrate in columns to ionize the gas filled in the space and generate electric discharge in the space. The scanning electrodes are scanned in sequence to write image signals applied to the signal electrodes in the optoelectric material.
In the plasma cell, a discharge voltage is applied between adjacent scanning electrodes, having opposed polarities, to ionize a gas and generate plasma discharge. To perform fast line-sequential scanning of the plasma cell, it is required that plasma discharge is generated quickly in response to application of a discharge voltage and that the plasma discharge decays quickly in response to the release of the discharge voltage. As an ionizable gas, an inert gas such as helium or neon has been used. Such a gas changes between the ground state and the excited state in response to application/release of a discharge voltage. The gas such as helium or neon, however, has a metastable state between the ground state and the excited state, and a part of the gas returns from the excited state to the ground state by way of the metastable state. This causes a problem that the decay of the plasma discharge is retarded, which makes it impossible to make the line-sequential scanning of a plasma cell faster. In particular, in the case of using a plasma cell for a monitor of a personal computer complying with an XGA standard or for a television monitor complying with an HDTV standard, there occurs a problem that fast line-sequential scanning, which is necessary for the monitor of this type, is obstructed by retardation of the decay of plasma discharge resulting from the above-described metastable state. The retardation of the decay of the plasma discharge causes initiation of the next operation of scanning electrodes in a state in which writing of image signals are not completed yet, and accordingly, it becomes difficult to carry out sufficient writing, thereby degrading the display contrast. Also the retardation of the decay of plasma discharge applies an unnecessary offset potential to the optoelectric material, resulting in a so-called burning in of a display screen.